package org.apache.lucene.search;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;
import java.util.BitSet;

import org.apache.lucene.index.IndexReader;

/**
 * Constrains search results to only match those which also match a provided
 * query.
 * 
 * <p>
 * This could be used, for example, with a {@link RangeQuery} on a suitably
 * formatted date field to implement date filtering. One could re-use a single
 * QueryFilter that matches, e.g., only documents modified within the last week.
 * The QueryFilter and RangeQuery would only need to be reconstructed once per
 * day.
 * 
 * @version $Id:$
 */
public class QueryWrapperFilter extends Filter {
	private Query query;

	/**
	 * Constructs a filter which only matches documents matching
	 * <code>query</code>.
	 */
	public QueryWrapperFilter(Query query) {
		this.query = query;
	}

	public BitSet bits(IndexReader reader) throws IOException {
		final BitSet bits = new BitSet(reader.maxDoc());

		new IndexSearcher(reader).search(query, new HitCollector() {
			public final void collect(int doc, float score) {
				bits.set(doc); // set bit for hit
			}
		});
		return bits;
	}

	public String toString() {
		return "QueryWrapperFilter(" + query + ")";
	}

	public boolean equals(Object o) {
		if (!(o instanceof QueryWrapperFilter))
			return false;
		return this.query.equals(((QueryWrapperFilter) o).query);
	}

	public int hashCode() {
		return query.hashCode() ^ 0x923F64B9;
	}
}
